METHODOLOGICAL INVESTIGATIONS ON DOC DETERMINATIONS BY THE HTCO METHOD

Results are presented on the function and use of the catalyst in the c ommonly employed high-temperature catalytic oxidation (HTCO) method fo r determination of organic carbon concentrations, The instrument used was a Shimadzu TOC 5000 analyzer with a 0.5% platinum-coated aluminum oxide catalyst, Some basic considerations on gas flow rates and volume s of the catalyst kiln, together with experiments using carrier gas wi th and without oxygen, led to the conclusion that O-2 is unlikely as t he source of reacted oxygen in the HTCO oxidation of organic carbon. R esults from injections of C-14-labelled organic material showed that n o residual carbon remains on the catalyst surface after a large number of injections, This indicates that the oxidation of organic carbon to gaseous compounds is complete and the catalyst is not a source of car ry over signal between injections. The blank signal from injection of water probably originates from carbonaceous compounds contained in the catalyst particles. A series of salt water injections (salinity 34.4) showed that > 2500 injections can be made without deterioration of ca talyst performance.